Need Electrical Help !!

[pixie]

hi gang,
Does anyone have any info about how to wire a breaker box correctly???

Moss is doing the electrical and is hung up on this part.Thanks !!-Pix

[pixie]

To be more specific, I am wondering about two things. First, does anyone have a simple diagram of where the wires go in a regular breaker box? Does it matter where the white and black cords go since it is alternating current? (I am speaking of the main wires not the ones conected to the individual breakers)
The second is about the relay on the batteries. There are two big terminals ,I know they are connected to the positive terminals of the baterys, but there is athird terminal on top . It is smaller and I assume it is a ground. Does it get ground to the bus or to one of the ground terminals? If it go's to one of the ground terminals, which one? Is it the battery I wish to start the vehicle with or is it the batterys I wish to power the electricity? Thanx for any help you can provide.
Moss,

[Steve]

I'll try to help but I have to admit I don't completely understand what you are asking.

The breaker box can go anywhere, preferably a central location so that you can run shorter wires to all the outlets. You can physically run your AC cables anywhere, keep in mind you don't want them to get creased, pinched, cut, or worn. If you mean, where should the main wires run; at most campsites the electrical hookup is on the left side. So put the plug for shore power on the left side of the bus.

I don't understand what you are asking about the batteries. Are you using a relay to turn on and off power from the batteries to the inverter? As for hooking up a three terminal relay, the two big terminals will connect between the source and destination of what you want to turn on and off. The third wire is called the signal wire, this activates the relay to connect and disconnect the two larger terminals. You will want to connect it to a switch, or a remote sender on another device to turn it on automatically.

[pixie]

Thanks for the reply!!

Actually, what I was asking about was where the black and white wires go in the breaker box not where the breaker box goes. There are two screws besides the grounding screw and I don't know If it matters where the white and black wires go.

The other problem I am having is that I am trying to isolate the starting battery from the reserve batterys. I was told to get a relay. Whenever I read about what I am trying to do , they mention the word Isolator. Are these two items the same thing or was I given bad advice ?? -Moss

[Steve]

Here is a guide on hooking up your breaker box:

Installing A Circuit Breaker

An isolator is NOT the same thing as a relay. A relay is an electronically activated switch. An isolator is a set of diodes that allow current to only flow in one direction. Here is a picture of the isolator in my bus:



The isolator will allow your alternator to charge both the engine battery, and battery bank without needing to be switched back and forth. It will also allow you to run your inverter off your bank and not have to worry about draining the engine battery because it will not allow current to flow in that direction.

[Roasting8]

Hi Pix and Moss,

The breaker box should be easy to connect. There are three connections in a breaker box, one is the Hot, another is the neutral, and the third is ground.

The easy thing about the box is that everything is that it's all color coded. The black wire goes to the brass colored connectors of the box (the connector that goes through the circuit breaker), the white goes to the lighter colored connector of the box, and the green goes to the green colored screw of the box.

When connecting the box, make sure that the box is not grounded to the bus chassis (isolate the box from any metal on the bus) and connect all of the green wires to that green wire.

I hope this makes sense but, if it doesn't, go to the nearest Home Depot and ask the guy in electrical, on how to connect the box.

I hope this helps.

[Roasting8]

Steve,

Thanks for the link, that should help them a lot.

[pixie]

You guys are awsome! Thanks for the info. -Pixie

[Bullwinkle]

I believe that you do want your AC box grounded to the bus body. If it were not, and the hot lead were to make contact with the body, your whole bus would have a 110 volt potential to ground – which would be a nasty surprise to anyone walking up and laying a hand on it….

What you don’t want is for the neutral (white) wire to be grounded to the body. A lot of the breaker boxes that you might buy in a Home Depot-type store will have a bolt you can install to short the neutral to the box (ground). If this were done on a box installed in a bus, some of the current that would normally flow through the neutral might decide to shortcut through someone touching the bus. Not as nasty as scenario #1, but it could still be hair-raising.

A. Moose

[Eric von Kleist]

Originally Posted by Bullwinkle

I believe that you do want your AC box grounded to the bus body. If it were not, and the hot lead were to make contact with the body, your whole bus would have a 110 volt potential to ground – which would be a nasty surprise to anyone walking up and laying a hand on it….

What you don’t want is for the neutral (white) wire to be grounded to the body. A lot of the breaker boxes that you might buy in a Home Depot-type store will have a bolt you can install to short the neutral to the box (ground). If this were done on a box installed in a bus, some of the current that would normally flow through the neutral might decide to shortcut through someone touching the bus. Not as nasty as scenario #1, but it could still be hair-raising.

A. Moose

THE INFORMATION BELOW ABOUT GROUNDING THE AC IS WRONG! YOU DO GROUND THE AC TO THE BUS. NEUTRAL SHOULD NOT BE BONDED TO THE GROUND, BUT THE AC SHOULD BE GROUNDED TO THE CHASSIS. Edit added after I went back and read the instruction manual again....

Negative, negative. Do NOT ground the AC to the bus body. RV's should have a "floating" ground. That is, the ground should ONLY connect to the ground through the ground on the shore power cord to the campgrounds ground at the campground's distribution box. You are absolutely correct that you do not want a hot or neutral wire to short out to the body. If you ground the bus body, there is a greater likelihood of YOU being the ground to the bus if you touch a hot wire. If you have no ground to the body, and touch a hot wire and the bus, there will be a less effective path for the electricity to follow.

First, there are two kinds of breaker boxes, "mains breaker" and "mains lug". The difference is that in one there is a big breaker on the incoming hot supply line(s), while with the other, the incoming hot supply lines are just screwed down with a lug (bolt), and there is no breaker between the bus and the "mains" (service line).

Inside the breaker box (distribution panel) there should be two bars with a bunch of screws in them. One is for ground, and one is for neutral. All the ground wires (including the incoming service ground) get hooked to the ground bar. All the neutral wires (including the incoming service line neutral) get hooked to the neutral bar. All of the hot wires get hooked to breakers (including the incoming service line hot wires).

Some breaker boxes give you an option to connect the ground terminals directly to the neutral terminals via an optional connecting do-hickey that swivels over from the ground to the neutral side. DON'T. The ground and neutral on the bus should remain completely separate. Be sure not to bolt the service box to any metal on the bus -- don't bolt it to a wood panel and run the bolts into the bus, either, as that's the same as bolting to the bus. Absolute separation.

Extremely good information on this topic in http://www.phrannie.org/battery.html . Phred recommends the following book:

"Another must-have book is "RV Electrical Systems" by Bill and Jan Moeller. With both AC and DC electrical systems and excellent 12 volt coverage, it is the best source I've seen on 120 volt AC systems. If it's not covered in this book, you can probably get along without it. The authors go into extraordinary detail without getting into engineering "lingo" and tell you things nobody else does (and those things many authors assume we already know--that we don't). With this book you won't be the dumbutt at a rally who miswires something and screws everybody else up. $19.95, 265 pages, detailed illustrations. In many bookstores, RV stores and from Amazon."

I got the book. WELL WORTH THE PRICE. Extremely valuable information. Saved me more than the price by just preventing me from making ignorant screw-ups.

[busone]

Eric is right don't bond the neutral and ground anywhere in the bus. It is very common mistake that can have very nasty results. If you are unsure of what you are doing this is one place to get professional help. Most home depot or lowes people will probably not know about wiring a bus. Normally in residential construction you do bond the ground and neutral but not on a bus. Make sure they are seperate. You should also use GFCI outlets or breakers in the kitchen and bath areas.

[Eric von Kleist]

One other suggestion regarding electrical. If you use Romex (brand name for solid copper house wiring) or any other solid wire, it is extremely important that you fasten the wire down to something solid every 8" or 12" or so. The vibrations from the bus traveling (or just idling) will cause sections of the wire to bend back and forth ever so slightly, and over time those sections will become work annealed (hardened and embrittled), and eventually they will fail, causing shorts and other problems.

I used little zip fasteners with a flange and hole for a screw, and I attached my wires securely. Honestly, I thought this was overkill, since I wouldn't be using the bus much for traveling, but I did it anyway. My son recently came to visit, and I checked the oil on his Cherokee. The dipstick tube came off in my hands! I had the engine rebuilt about 4 years ago, and apparently the mechanics never secured the mount on the upper end of the dipstick tube back to the engine block. Over time that tube has just been vibrating back and forth, with the vibrations focused on the location where it attaches to the engine block. The tube was maybe 3/64" inch sheet metal, and it snapped clean off at the engine block from metal fatigue caused by the vibrations.

I'm glad I was so fastidious about tightening down my wiring.

Stranded wiring is not as susceptible to this problem as solid wiring, but it should still be tied down in some fashion. Also, wrap your DC wiring around itself (negative around positive) if you run two wires for your DC circuits (instead of connecting to ground on the bus body). If you do this, the currents cancel out each other's electromagnetic fields to a large degree. These fields can cause radio-frequency interference in many situations. AC wiring does not cause this problem, just DC wiring.

[Bullwinkle]

Well, it seems that everyone agrees that you want a floating neutral. On the subject of floating the ground, I remain convinced that it is a bad practice.

It is true, as Eric pointed out above, that leaving the body ungrounded could save a person a shock if they were to touch a hot wire and the body. However, this isn’t a very compelling scenario -- people don’t generally touch hot wires by accident, for these are all kept locked away. Good electrical practice generally aims to prevent accidental electrocution: the person who opens up a live electrical box and starts pulling out hot wires is on their own.

On the other hand, even though they are locked away where you can’t accidentally touch them, one of those hot wires could suffer an insulation failure, and become shorted to the frame. This is not unlikely in the long run: the vibration of driving down the road can cause a lot of chaffing on the wiring. If such a short happens in a bus with a grounded body, then a circuit-breaker goes “pop”, and it’s time to find the problem and fix it. If it happens on a bus with a floating ground, then the entire body would suddenly have a 110 volt potential to ground. Since everything would keep right on working, this problem might persist unnoticed for a long time – until someone discovered it the hard way – say by walking up to your bus with bare feet and touching it.

If someone knows a more compelling reason why a bus body shouldn’t be grounded, I would appreciate hearing it. In the meantime, it is a comfort to me when I walk up to my bus to know that it is at ground potential, and I won’t be electrocuted when I touch it.

A. Moose

[pixie]

Thank you guys,I really appreciate your help in keeping us un electrocuted.

Moss has another question here,

what about grounding the inverter.?? He grounded it to the bus chasis,and wants to know ,before he turns it all on,was that a good idea ??

Are there any other safety issues we should know about ?? - Pixie

[Roasting8]

A. Moose,

You're absolutely right; the green wire should be grounded to chassis ground. Don't mind me, I had a brain fart.

Robert

[captainkf]

My ac is grounded to the bus and it works great. My inverter's negative comes from the batteries which are in turn mounted to the frame. Hope this helps. -Richard

[Eric von Kleist]

One thing that I can see that could potentially be a problem is that by grounding the AC to the frame, you link the AC and DC systems through the DC/AC ground. I don't know if this matters at all, but it doesn't sound like a good idea. I don't know enough about electrical things to tell.

On the DC side, I'm keeping my bus and house systems entirely isolated. I know that is overkill, and not necessary at all. I'm running negative and positive wires to all the DC outlets and appliances. It means 2x as much in wiring costs, as well. I'm using 8 gauge stranded wire for the DC wiring. I don't have any large loads on the DC circuits -- the water pump is the biggest right now, and I don't forsee using any large DC loads in the future, as all DC lighting will (eventually) be florescent.

Oh, you might think about using 12VDC florescent "worklights" for lighting. They don't cost too much, and usually they have a magnet on them that will hold them to the bus ceiling, which means you can plug them into a DC socket and then move them around at your convenience, kind of like an area lamp. Shoot, you could probably disassemble the worklight body and put the guts into a nice lamp of some kind if you wanted to.

[captainkf]

from all the research I have done, grounding the ac in the bus is the safest way to go. I installed my dc with dual strand wire and it is grounded in one place. This way I can control the system if changes are made later on. So far, so good.

However, opinions are like a**holes, everyones got one.

-Richard

[Steve]

This doesn't make it right, but for the record I have my DC and AC both grounded to the bus.

If you are worried about electrocution why not just ground your bus with a grounding stake.

[Eric von Kleist]

I was wrong about the grounding. I posted a separate thread with that info so the information would be in the thread topic. The AC should be grounded to the bus. Only the neutral should be floating (not bonded to the bus or the ground). I even had the information highlighted in my copy of RV Electrical Systems, so I don't know how I got it into my head that both neutral and ground should be floating, but I was very meticulous to do it absolutely wrong! I'm going to hook up a grounding wire like muy pronto !

Sorry for the disinformation, and thanks for raising the question, otherwise I never would have gone back and looked it up.